Kernel panic

Can anyone help me please. I have an imac, went to shut it down this morning (due to an internet problem) and it told me I had four items downloading... I had no idea what they were and couldn't quit out of it so hit the power button. On turning the computer back on my screen went grey and a whole lot of text came up on my screen ending in Darwin Kernel version 9.6.0. There is also a black box in the centre of the screen saying you need to restart your computer. Hold down the Power button for several seconds or press the restart button (in four languages).
I've tried shutting down, restarting, holding down the option+control+p+r keys, restarting with the shift L key, pulling the power cord out.... nothing works. I also saw a couple of suggestions to type where the cursor is but it won't let me.

Does anyone have a solution for me before I go into panic mode, please?

It sounds as though your computer was installing system updates via the 'Software Update' mechanism. If that's the case, you've likely broken the OS by interrupting it.

A kernel panic is a little different. Instead of seeing the CLI, you would still see the GUI, but it would dim and you'd get a message that your computer needs to restart. Typically a kernel panic is indicative of a hardware problem or a damaged OS. In your case, it doesn't even sound like it can boot completely.

Assuming you don't have a backup and you have data you need to recover, you'll either have to connect the Mac to another and use Target Disk Mode to retrieve your data. Alternatively, you could remove the hard disk and hook it up externally elsewhere, but that's not really a simple proposition given the way the iMac is put together.

So, once you've got your data recovered, you'll need to boot from your System Disc 1 and format the hard drive and reinstall. When finished, you can then restore your data to the newly reinstalled drive.

Rule 6: NEVER interrupt a computer while its doing updates! EVER!!